In the prior art, there has been developed a type of seal commonly referred to as a bulb seal. Such seal generally consists of a mount section formed of a thermoplastic material and a bonded bulb section formed of an elastomer material. Typically, such seals are formed by means of a dual durometer extrusion process. An example of such a seal is illustrated in FIG. 1. As shown, such a seal includes a mount section 11 having a substantially inverted U-shaped configuration with a pair of laterally extending, transversely aligned portions 12 and 13, formed of a thermoplastic material, and a bulb section 14 formed of a thermoplastic elastomer, bonded to the upper end of the mount section and having a polygonal cross-sectional configuration. Such seals widely have been used as hood-to-cowl seals in the automotive industry. To reduce the cost of such seals, a filler often is used in the thermoplastic material used to form the mount section of such seals.
In the production of such seals utilizing such materials and an extrusion forming process, however, it has been found that the use of fillers in the thermoplastic materials used to form the mount sections of the seal results in shrinkage of such sections which further results in certain distortions of the bulb section, often referred to as “smiles.” To eliminate such distortions of the bulb sections of such seals, it has been a practice of using less filler in the thermoplastic material forming the mount sections of such seals which has had the effect of increasing the costs.
It thus is the principal object of the present invention to provide a seal of the type described in which increased amounts of filler may be used in the thermoplastic material used to form the mount sections of such seals, in order to reduce cost, while eliminating shrinkage of the mount sections which would otherwise cause a deformation of the shape of the bulb sections of such seals.